The existence of peripheral vascular serotonergic receptors (5HT.sub.2 type) has recently been demonstrated. The vascular receptor mediating serotonin-induced contraction has now been demonstrated to be of the 5HT.sub.2 subtype in rat aorta, caudal artery and jugular vein.
Recently, also, it has been postulated that ketanserin, a potent antagonist of 5HT.sub.2 vascular receptors, acts to lower blood pressure through blockade of these receptors. However, ketanserin also has a high affinity for alpha.sub.1 receptors such as that found with phentolamine, another blood pressure lowering agent. At present, there have been no pure peripheral vascular serotonergic receptor blockers available to determine whether such blockade alone would result in anti-hypertensive activity.